Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $88.28   9.556%   $96.716   $96.72   $96.70   $96.70  
  Purchase #2 $34.26   7.118%   $36.6986   $36.70   $36.70   $36.70  
  Purchase #3 $212.29   4.582%   $222.0171   $222.02   $222.00   $222.00  
  Purchase #4 $156.91   7.563%   $168.7771   $168.78   $168.80   $168.80  
  Purchase #5 $94.33   7.864%   $101.7481   $101.75   $101.75   $101.70  
  Purchase #6 $190.82   5.663%   $201.6261   $201.63   $201.65   $201.60  
  Purchase #7 $216.84   4.849%   $227.3546   $227.35   $227.35   $227.40  
  7 purchase totals = $993.73       $1,054.9376   $1,054.95   $1,054.95   $1,054.90